Things of Middle-earth

Translations from the Elvish

In the evening they went to say good-bye to Bilbo. ... Then he gave Frodo his mithril-coat and Sting, forgetting that he had already done so; and he gave him also three books of lore that he had made at various times, written in his spidery hand, and labelled on their red backs: Translations from the Elvish, by B.B.

The Return of the King, LoTR Book 6, Ch 5, Many Partings

This account of the end of the Third Age [The Lord of the Rings] is drawn mainly from the Red Book of Westmarch. ... It was in origin Bilbo's private diary, which he took with him to Rivendell. ... But annexed to it and preserved with it, probably in a single red case, were the three large volumes, bound in red leather, that Bilbo gave to him [Frodo] as a parting gift. ...

But the chief importance of Findegil's copy [of the Red Book] is that it alone contains the whole of Bilbo's 'Translations from the Elvish'. These three volumes were found to be a work of great skill and learning in which, between 1403 and 1418, he had used all the sources available to him in Rivendell, both living and written. But since they were little used by Frodo, being almost entirely concerned with the Elder Days, no more is said of them here.